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This question is about water - AQA - GCSE Chemistry - Question 4 - 2016 - Paper 3
Question 4
This question is about water. Hard water contains dissolved compounds. Explain one benefit of drinking hard water. What is the name of the solid formed when hard w... show full transcript
Worked Solution & Example Answer:This question is about water - AQA - GCSE Chemistry - Question 4 - 2016 - Paper 3
Step 1
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Using temporary hard water in an electric kettle reduces the efficiency of the kettle. Describe how this happens.
Answer
Temporary hard water predominantly contains calcium hydrogen carbonate. When heated or boiled in a kettle, this compound decomposes to form calcium carbonate, which precipitates out of the solution. This solid forms a scale that coats the heating element and the kettle's interior, thereby insulating the heating element and reducing energy transfer to the water, which ultimately decreases the kettle's efficiency.
Step 4
Explain how an ion exchange resin changes the dissolved compounds in tap water to improve the water.
Answer
Ion exchange resins used in water filters typically contain sodium or hydrogen ions. When hard water passes through the resin, these ions exchange places with the calcium and magnesium ions in the water. This process effectively removes the hardness-causing ions, leading to softened water. While this improves the taste and quality of the water, it does not significantly alter reactivity, ensuring that the water remains safe for consumption.